Electromagnetic device



ober% ATTORNEY 2 Sheets-Sheet 1 ELECTROMAGNETIC DEVICE c. w SPAULDING ETAL April 21, 1959 Filed Jan. 51, 1957 v w Lg INVENTORS CharlesW.Spcu'|ding 8 I WITNESSES: U 25% A ril 21, 1959 c.-w. SPAULDING ET AL3,

ELECTROMAGNETIC DEVICE I Filed Jan. 31, 1957 2 Sheets-Sheet 2 Fig.2.

United States Patent Q ELECTROMAGNETIC DEVICE Charles W. Spaulding andRobert A. Pelz, Beaver, Pa., assignors to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication January 31, 1957, Serial No. 637,384

7 Claims. (Cl. 200-87) Our invention relates, generally, toelectromagnetic devices and, more particularly, to electromagneticrelays,

and contactors which are utilized as motor starters.

Heretofore, motor starters have been so constructed that the contactmembers of a starter are opened as a result of a drop in the linevoltage. In the interest of safety it is the usual practice to connect amotor starter for non-automatic or manual reclosing. Therefore, when astarter drops open, power to the machine or machines controlled by thestarter is interrupted until the starter is reclosed manually. In somecases, the reclosing of starters is the duty of people other than themachine op erators, which results in a considerable loss of productron.

An object of our invention is to provide a means for holding anelectromagnetic device closed during momentary dips in the controlvoltage.

Another object of our invention is to provide a low voltage holdingattachment for an electromagnetic device which may be readily installedon the device when desired.

A further object of our invention is to provide for adjusting thedropout voltage of an electromagnetic contactor or relay.

Other objects of our invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of our invention, a permanent magnet,which is clamped between two pole pieces, is mounted on the stationarybase for the arc box of an electromagnetic contactor or starting relayfor a motor. An armature for the magnet is attached to the cross bar ormember of the starter which carries the movable contact members of thestarter. When the contact members are closed, the armature is broughtinto contact with the pole pieces of the permanent magnet. Theadditional holding force provided by the permanent magnet causes themain contact members to remain closed at a relatively low voltage on theoperating coil of the starter, thereby preventing the motor controlledby the starter from being disconnected during momentary dips in the linevoltage. The dropout voltage may be adjusted by means of shunting screwswhich vary the reluctance of the magnetic path of the permanent magnet.

For a better understanding of the nature and objects of the invention,reference may behad to the following detailed description, taken inconjunction with the accompanying drawing, in which:

Figure 1 is a view, in side elevation, of an electromagnetic contactorembodying the principal features of the invention;

Fig. 2 is a view, in section, of a portion of the contactor shown inFig. 1;

Fig. 3 is a view partly in plan and partly in section, showing thepermanent magnet mounted on the contactor;

Fig. 4 is a view, in elevation, of the base for the permanent magnet;

2,883,487 I a-tented Apr. 21, 1959 Fig. 5 is a view, in elevation, ofthe permanent magnet, and

Fig. 6 is a view, in elevation, of one of the pole pieces for thepermanent magnet.

Referring to the drawings and particularly to Figs. 1 and 2, the motorstarter or contactor shown therein is of the electromagnetic type andcomprises an electromagnet 10, an armature 11, a contact carrier orcross bar 12, an arc box 13, an insulating base 14, and a sheet metalpan or base 15. The pan 15 may be mounted on any suitable supportingstructure such as a switchboard panel or it may be mounted in anenclosing cabinet. The electromagnet 10 is mounted on a base 16 which isattached to the pan 15 by means of brackets 17 and 18.

A coil 19, which may be energized from a suitable power source of apredetermined voltage, is provided for the electromagnet 10. Thearmature 11 is pivotally mounted on the bracket 18 which functions as abearing member for the armature 11. A kickout spring 21 biases thearmature 11 to the open position when the coil 19 is deenergized. Whenthe coil is energized, the armature 11 is actuated to the closedposition, thereby causing a bridging contact member 22, which is carriedby the cross bar or carrier 12, to engage stationary contact members 23and 24. As shown more clearly in Fig. 2, the stationary contact member23 is attached to a terminal member 25. The stationary contact member 24is attached to a terminal member 26. The terminal members 25 and 26 aremounted on the insulating base 14 which is attached to the supportingpan 15.

As shown in Fig. 2, the bridging contact member 22 is mounted in a yokeor saddle 27 which is attached to the cross bar or carrier 12. A spring28 is mounted in the saddle 27 to maintain a predetermined contactpressure between the bridging contact member 22 and the stationarycontact members 23 and 24 when the contact members are closed. The crossbar 12 is preferably composed of insulating material. Likewise, the arcbox 13 is composed of an insulating material. As shown, the arc box 13may be provided with a plurality of spaced metal plates 29 which assistin a manner well known in the art in interrupting the are drawn betweenthe contact members when opened.

As explained hereinbefore, the contact members of a contactor or motorstarter of the type previously constructed have been opened duringmomentary dips in the voltage of the power source which energizes thecoil 19. Heretofore the contact members have been opened when thecontrol voltage is reduced to approximately 50% of the normal ratedvoltage. As also explained hereinbefore, it is customary to so connectmotor starters that they must be reclosed manually after having beenopened by a reduction in voltage. This is done for safety reasons inorder to protect personnel who are Working around the apparatus drivenby the motors controlled by the motor starters. The time required toreclose the starters results in a needless loss in production in casethe dip in voltage is of a short duration which would not affect theoperation of the motors.

In order to prevent the starter from being opened by a momentary dip inthe operating voltage, we have provided a holding attachment forretaining the contact members of the starter closed at a still lowermomentary reduction in the applied voltage. As shown in Figs. 1 and 3, apermanent magnet assembly 31 is attached to the base 14 at one side ofthe arc box 13. An armature 32 is attached to an extension 33 on thecarrier 12. The magnet assembly 31 comprises a permanent magnet 34 whichis clamped between two pole pieces 35 by means of screws 36. The polepieces 35 may be soldered or otherwise secured to a base 37. The base 37is attached 3 to the insulating base 14 of the contactor by means ofscrews 33. The pole pieces 35 are composed of a magnetic material andthe base 37 is preferably composed of a non-magnetic material.

As shown more clearly in Fig. 1, the armature 32 is of a .i-shape. Theshort leg of the J is attached tothe extension 33 of the cross bar 12 bymeans of screws 39. Thus, the armature 32 is of a spring-likeconstruction and the long leg of the armature may deflect slightly whenit is actuated into engagement with the pole pieces 35 of the magnetassembly 31. In this manner, the armature 32 does not interfere with theclosing of the main contact members of the starter by the operation ofthe cross bar 12 which is attached to the armature 11 of theelectromagnet 10. When the armature 32 engages the polepieces 35 theadded force provided by the attraction of the armature, 32 to thepermanent magnet assembly 31 enables the main contact members. of thestarter to remain closed during momentary dips in the operating voltage.

In order to provide for adjusting the voltage at which the contacts ofthe starter will open, part or all of the screws 36 may be composed ofmagnetic material. By making the screws magnetic and then removing orreplacing part of them with non-magnetic screws the re luctance of themagnetic path of the. permanent magnet may be varied, thereby providingfor adjustment of the dropout voltage. The utilization of a holdingattachment of the present type enables the dropout voltage to be reducedto zero if desired. As previously explained, the

dropout voltage may be adjusted by means of the shunting screws 36 whichfunction as a magnetic bridge between the magnetic pole pieces 35 of themagnet assembly. The number of the screws which are of magnetic materialmay be varied to adjust the dropout voltage to approximately any valuebetween zero and the dropout voltage that would be normal Withoutpermanent magnet attachment.

From the foregoing description, it is apparent that we have provided arelatively simple and inexpensive attachment for electromagneticcontactors and motor starters which provides a means for holding theelectro-magnetic device closed during momentary. dips in the operatingvoltage, thereby avoiding costly and unnecessary interruptions in theoperation of the machines driven by the motors controlled by motorstarters. The holding device is so constructed that it may be readilyattached to an electromagnetic contactor when the contactor ismanufactured or after it is installed in service.

Since numerous changes may be made in the above described constructonand different embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all the mattercontained in the foregoing description or shown in the ac-- companyingdrawings shall be interpreted as illustrative and not in a limitingsense.

We claim as our invention:

1. In an electromagnetic device, in combination, a base, a stationarycontact member supported by the base, a movable contact member forengaging the stationary contact member, a carrier for the movablecontact member, an electromagnet having an armature for actuating thecarrier to close said contact members to conduct current therethrough, apermanent magnet mounted on the base, an armature for the permanentmagnet, said armature being separate from the armature for the electromagnet and actuated by said carrier to a position. in which theattraction of the permanent magnet for its armature assists theelectromagnet in holding-the contact members closed. after they havebeen closed. by the electromagnet, and said permanent magnet functioningindependently of the current flowinglthrough said contact members.

2. In an electromagnetic device, in combination, a

4 base, a stationary contact member supported by the base, a movablecontact member for engaging the stationary contact member, an arc boxattached to said base and substantially enclosing said contact members,a carrier for the movable contact member, an electromagnet having anarmature for actuating the carrier to close said contact members toconduct current therethrough, a permanent magnet mounted on the baseexternally of said arc box, an armature for the permanent magnet, saidarmature being separate from the armature for the electromagnet andattached to the carrier and actuated by said carrier to a position inwhich the attraction of the permanent magnet for its armature assiststhe electromagnet in holding the contact members closed after they havebeen closed by the electromagnet, and said permanent magnet beingdisposed to function independently of the current flowing through saidcontact members.

3. In an electromagnetic device, in combination, a base, a stationarycontact member supported by'the base, a movable contact member forengaging the stationary contact member, a carrier for the movablecontact memher, an electromagnet having an armature for actuating thecarrier to close said contact members to conduct current therethrough, apermanent magnet mounted on the base, a spring type armature for thepermanent magnet, said armature being separate from the armature for theelectromagnet and actuated by saidcarrier to engage the permanent magnetwhereby the attraction of the permanent magnet for its armature assiststhe electromagnet in holding the contact members closed after they havebeen closed by the electromagnet, and said permanent magnet beingdisposed to function independently of the current flowing through saidcontactmembers.

4. In an electromagnetic device, in combination, a base, a stationarycontact member supported by the base, a movable contact member forengaging the stationary contact member, a carrier for the movablecontact member, an electromagnet having a magnetic circuit and anarmature for actuating the carrier to close said contact members toconduct current therethrough, a permanent magnet disposed between twospaced pole pieces mounted on the base, said pole pieces'providing amagnetic circuit separate from the magnetic circuit. for theelectromagnet, a spring: type armature for the permanent magnet, saidarmature for the permanent magnet being actuated. by said carrier toengage-the pole pieces whereby the attraction of the permanentimagnetforthe armature assists the electromagnet in holding the contact membersclosed after they have been closed by the electromagnet, and said.permanent magnet being disposed to function independently of theycurrent flowing. through said contact members.

5. In an electromagnetic device, in. combination, a base, a stationarycontact member supported by the base, a movable contact member forengaging the stationary contact member, a carrier for the movablecontact memher, an electromagnet having a. magnetic circuit and anarmature for actuating. the carrier to close said contact members, apermanent magnet disposed between two spaced-pole pieces mounted on thebase, said pole pieces providinga magnetic circuit separate from themagnetic circuit for the electromagnet, a spring type armature for thepermanent magnet, said armature, for the permanent magnet being actuatedby said carrier to engage the pole pieces whereby the attraction of thepermanent magnet for the armatureassists the electromagnet in holdingthecontact members closed after they have been closed by the electromagnet,and magnetic material; means bridging said pole pieces to adjust theattraction of the permanent magnet for said armature.

6. In an electromagnetic device, in combination, a base, a stationarycontact member supported by the base, a movable contact member forengaging th tionary contact member, a carrier for the movable contactmember, an electromagnet having a magnetic circuit and an armature foractuating the carrier to close said contact members, a permanent magnetdisposed between two spaced pole pieces mounted on the base, said polepieces providing a magnetic circuit separate from the magnetic circuitfor the electromagnet, a spring type armature for the permanent magnet,said armature for the permanent magnet being actuated by said carrier toengage the pole pieces whereby the attraction of the permanent magnetfor the armature assists the electromagnet in holding the contactmembers closed after they have been closed by the electromagnet, andscrews for clamping the pole pieces against the permanent magnet, thenumber of said screws being variable to vary the reluctance of themagnetic path of the magnet thereby adjusting the attractive force onthe armature.

7. In an electromagnetic device, in combination, an insulating base, astationary contact member supported by the base, a movable contactmember for engaging the stationary contact member, a carrier for themovable contact member, an electromagnet having a magnetic circuit andan armature for actuating the carrier to close said contact members whenthe electromagnet is energized by a predetermined voltage, a permanentmagnet .6 disposed between two spaced pole pieces mounted on the base,said pole pieces providing a magnetic circuit separate from the magneticcircuit for the electromagnet, a J-shaped armature for the permanentmagnet, the short leg of the J-shaped armature being attached to saidcarrier and the long leg of the armature being actuated into engagementwith said pole pieces when the contact members are closed, whereby thepermanent magnet assists the electromagnet in holding the contactmembers closed during momentary dips in the voltage on theelectromagnet.

References Cited in the file of this patent UNITED STATES PATENTS1,298,746 Lum Apr. 1, 1919 1,918,232 Baker et a1. July 11, 19332,432,899 lmrnel Dec. 16, 1947 2,467,720 Austin Apr. 19, 1949 2,539,547Mossman et a1 Jail. 30, 1951 2,542,835 Pierce Feb. 20, 1951 2,550,110Ellis Apr. 24, 1951 2,594,088 Sonnemann et al. Apr. 22, 1952 2,679,561Thompson May 25, 1954

